title: Immobilization-induced hypersensitivity associated with spinal cord sensitization during cast immobilization and after cast removal in rats.
abstract: This study examined mechanical and thermal hypersensitivity in the rat hind paw during cast immobilization of the hind limbs for 4 or 8 weeks and following cast removal. Blood flow, skin temperature, and volume of the rat hind paw were assessed in order to determine peripheral circulation of the hind limbs. Sensitization was analyzed by measuring the expression of the calcitonin gene-related peptide (CGRP) in the spinal dorsal horn following cast immobilization. Two weeks post immobilization, mechanical and thermal sensitivities increased significantly in all rats; however, peripheral circulation was not affected by immobilization. Cast immobilization for 8 weeks induced more serious hypersensitivity compared to cast immobilization for 4 weeks. Moreover, CGRP expression in the deeper lamina layer of the spinal dorsal horn increased in the rats immobilized for 8 weeks but not in those immobilized for 4 weeks. These findings suggest that immobilization-induced hypersensitivity develops during the immobilization period without affecting peripheral circulation. Our results also highlight the possibility that prolonged immobilization induces central sensitization in the spinal cord.
authors.affiliation: Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki, 852-8520, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Hamaue
authors.forename: Jiro
authors.initials: J
authors.lastname: Nakano
authors.forename: Yuki
authors.initials: Y
authors.lastname: Sekino
authors.forename: Sayaka
authors.initials: S
authors.lastname: Chuganji
authors.forename: Jyunya
authors.initials: J
authors.lastname: Sakamoto
authors.forename: Toshiro
authors.initials: T
authors.lastname: Yoshimura
authors.forename: Tomoki
authors.initials: T
authors.lastname: Origuchi
authors.forename: Minoru
authors.initials: M
authors.lastname: Okita
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000096:biosynthesis; D006614:Hindlimb / Q000098:blood supply / Q000503:physiopathology*; D006930:Hyperalgesia / Q000503:physiopathology*; D007103:Immobilization / Q000009:adverse effects*; D051381:Rats; D012881:Skin Temperature; D013116:Spinal Cord / Q000503:physiopathology*
chemical_list: D015740:Calcitonin Gene-Related Peptide